RFR 8170289: Re-examine entry point support in jlink

[Mandy Chung]

 282                     throw new RuntimeException(module + " does not have main class: " + mainClassName);

- Throwing IllegalArgumentException would probably be better.

 101 err.launcher.value.format:launcher value should be of form <command>=<module>: {0}

- should this message include optional main class; something like <command>=<module>[/<main-class>]

This validation is done after the image is created.  Can you file a JBS issue to separate the launcher file creation and the validation from image creation?  That can be improved in the future.

Otherwise, looks okay.  No need to send a new webrev.  

Mandy
P.S. There is some issue to access cr.openjdk.java.net. I got a copy of webrev.02 from Sundar to review.

> On Dec 18, 2016, at 7:29 AM, Sundararajan Athijegannathan <sundararajan.athijegannathan at oracle.com> wrote:
> 
> Updated it: http://cr.openjdk.java.net/~sundar/8170289/webrev.02
> 
> Thanks,
> -Sundar
> 
> On 17/12/16, 12:33 AM, Mandy Chung wrote:
>>> On Dec 16, 2016, at 8:36 AM, Sundararajan Athijegannathan<sundararajan.athijegannathan at oracle.com>  wrote:
>>> 
>>> Hi,
>>> 
>>> Please review http://cr.openjdk.java.net/~sundar/8170289/webrev.01/ for https://bugs.openjdk.java.net/browse/JDK-8170289
>> 
>>  273             Optional<String>  mainClass = ModuleDescriptor.read(stream).mainClass();
>>  274             if (mainClass.isPresent()) {
>>  275                 mainClassName = mainClass.get();
>>  276             }
>> 
>> This should set mainClassName only if the main class is not specified
>> in the -—launcher option.  One may want to create launchers for
>> multiple entry points.
>> 
>> I think it should validate if the main class is present in the image.
>> If not found, it should output an error.
>> 
>> Something to be considered in a future release - the existing implementation
>> creates the launcher scripts as a special case in DefaultImageBuilder.
>> It seems cleaner to keep DefaultImageBuilder just for the image creation,
>> i.e. simply write out entries of the ResourcePool to the image.
>> The launchers could be added to the ResourcePool entries to the
>> corresponding module by one builtin plugin implementation.
>> 
>> For this issue, keeping the change to minimal is good.
>> 
>> Mandy
>> 
>>